This invention relates to a biochemical device and method for the determination of dissolved gases in solution. More particularly, this invention relates to a dry electrode/sample interface for discrete clinical analysis with an oxygen-sensing electrode.
Oxygen-sensing electrodes which measure dissolved oxygen in solution are well-known. The Clark pO.sub.2 electrode described in U.S. Pat. No. 2,913,386 is typical. In this electrode, oxygen diffuses through a gas-permeable membrane and is reduced at a platinum cathode which is kept at a fixed potential with respect to a silver-silver chloride reference anode.
Such electrodes have been used for a variety of biochemical determinations useful in clinical diagnosis. For example, the determination of blood glucose levels has been made with an oxygen-sensing electrode by measuring the oxygen uptake in a glucose oxidase enzyme catalyzed reaction. Illustrative of such use of the Clark pO.sub.2 electrode are the report by Kunz and Stastny, Clin. Chem. 20, 1018-22 (1974) and the review article by Gough and Andrade, Science 180, 380-84 (1973).
In use of the oxygen-sensing electrode, the sample reagent solution to be analyzed comes into contact with the electrode through a plastic membrane which is permeable to oxygen but impermeable to water and electrolytes. The desirability of constructing the electrode so that the membrane precludes any contact between the reagent sample to be analyzed and the electrolyte has been recognized heretofore. This is generally accomplished by forming a barrier with the membrane which is held in place at one end of the electrode with O-rings as described, for example, in U.S. Pat. Nos. 2,912,386 and 3,542,662, or sealingly positioned over the electrolyte chamber as disclosed in U.S. Pat. No. 3,334,039, or clamped in mounting discs as taught in U.S. Pat. No. 3,445,369. However, in these oxygen-sensing devices, the electrode still comes into contact with the reagent sample. A system whereby the electrode does not come into contact with the reagent sample would provide the advantage of freedom from sample carryover onto the electrode, and thereby, eliminate problems of cross contamination and need for washing after every sample analysis.